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《矿物冶金与材料学报》2021,28(12):2001-2007
Graphene oxide (GO) wrapped Fe3O4 nanoparticles (NPs) were prepared by coating the Fe3O4 NPs with a SiO2 layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO2 coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO2 on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO2 layer can effectively induce the GO nanosheets to completely wrap the Fe3O4 NPs, forming a core-shell Fe3O4@SiO2@GO composite where Fe3O4@SiO2 NPs are firmly encapsulated by GO nanosheets. The optimized Fe3O4@SiO2@GO sample exhibits a high saturated adsorption capacity of 253 mg·g?1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents. 相似文献
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《矿物冶金与材料学报》2021,28(12):1908-1916
The effect of CaCO3, Na2CO3, and CaF2 on the reduction roasting and magnetic separation of high-phosphorus iron ore containing phosphorus in the form of Fe3PO7 and apatite was investigated. The results revealed that Na2CO3 had the most significant effect on iron recovery and dephosphorization, followed by CaCO3, the effect of CaF2 was negligible. The mechanisms of CaCO3, Na2CO3, and CaF2 were investigated using X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS). Without additives, Fe3PO7 was reduced to elemental phosphorus and formed an iron–phosphorus alloy with metallic iron. The addition of CaCO3 reacted with Fe3PO7 to generate an enormous amount of Ca3(PO4)2 and promoted the reduction of iron oxides. However, the growth of iron particles was inhibited. With the addition of Na2CO3, the phosphorus in Fe3PO7 migrated to nepheline and Na2CO3 improved the reduction of iron oxides and growth of iron particles. Therefore, the recovery of iron and the separation of iron and phosphorus were the best. In contrast, CaF2 reacted with Fe3PO7 to form fine Ca3(PO4)2 particles scattered around the iron particles, making the separation of iron and phosphorus difficult. 相似文献
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《矿物冶金与材料学报》2020,27(4):472-482
Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method, which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method. In this study, the effect of the silica saturation coefficient (x) on the carbonation of hydrogarnet was investigated from the kinetic perspective. The results indicated that the carbonation of hydrogarnets with different x values (x = 0.27, 0.36, 0.70, and 0.73) underwent two stages with significantly different rates, and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3. The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and 14.80–34.84 kJ/mol, respectively. Moreover, the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion. 相似文献
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《矿物冶金与材料学报》2020,27(10):1347-1352
A new method of high-gravity combustion synthesis (HGCS) followed by post-treatment (PT) is reported for preparing high-performance high-entropy alloys (HEAs), Cr0.9FeNi2.5V0.2Al0.5 alloy, whereby cheap thermite powder is used as the raw material. In this process, the HEA melt and the ceramic melt are rapidly formed by a strong exothermic combustion synthesis reaction and completely separated under a high-gravity field. Then, the master alloy is obtained after cooling. Subsequently, the master alloy is sequentially subjected to conventional vacuum arc melting (VAM), homogenization treatment, cold rolling, and annealing treatment to realize a tensile strength, yield strength, and elongation of 1250 MPa, 1075 MPa, and 2.9%, respectively. The present method is increasingly attractive due to its low cost of raw materials and the intermediate product obtained without high-temperature heating. Based on the calculation of phase separation kinetics in the high-temperature melt, it is expected that the final alloys with high performance can be prepared directly across master alloys with higher high-gravity coefficients. 相似文献
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《矿物冶金与材料学报》2020,27(7):980-986
We report the picosecond laser ablation of aluminum targets immersed in a polar organic liquid (chloroform, CHCl3) with ~2 ps laser pulses at an input energy of ~350 μJ. The synthesized aluminum nanoparticles exhibited a surface plasmon resonance peak at ~340 nm. Scanning electron microscopy images of Al nanoparticles demonstrated the spherical morphology with an average size of (27 ± 3.6) nm. The formation of smaller spherical Al nanoparticles and the diminished growth could be from the formation of electric double layers on the Al nanoparticles. In addition to spherical aluminum nanoparticles, triangular/pentagonal/hexagonal nanoparticles were also observed in the colloidal solution. Field emission scanning electron microscopy images of ablated Al targets demonstrated laser induced periodic surface structures (LIPSSs), which were the high spatial frequency LIPSSs (HSF-LIPSSs) since their grating period was ~280 nm. Additionally, coarse structures with a period of ~700 nm were observed. 相似文献
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Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting (CC) molds with narrow widths for the production of automobile exposed panels. Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process. The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold. Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone. The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min?1 and casting speed of 1.7 m·min?1. Under the present experimental conditions, the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm. 相似文献
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Electroslag remelting (ESR) gives a combination of liquid metal refining and solidification structure control. One of the typical aspects of liquid metal refining during ESR for the advanced steel and alloy production is desulfurization. It involves two patterns, i.e., slag–metal reaction and gas–slag reaction (gasifying desulfurization). In this paper, the advances in desulfurization practices of ESR are reviewed. The effects of processing parameters, including the initial sulfur level of consumable electrode, remelting atmosphere, deoxidation schemes of ESR, slag composition, melting rate, and electrical parameters on the desulfurization in ESR are assessed. The interrelation between desulfurization and sulfide inclusion evolution during ESR is discussed, and advancements in the production of sulfur-bearing steel at a high-sulfur level during ESR are described. The remaining challenges for future work are also proposed. 相似文献
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Mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al2O3?Na2O system during high-temperature sintering
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《矿物冶金与材料学报》2020,27(7):924-932
The mineral transition and formation mechanism of calcium aluminate compounds in CaO?Al2O3?Na2O system during the high-temperature sintering process were systematically investigated using DSC?TG, XRD, SEM?EDS, FTIR, and Raman spectra, and the crystal structure of Na4Ca3(AlO2)10 was also simulated by Material Studio software. The results indicated that the minerals formed during the sintering process included Na4Ca3(AlO2)10, CaO·Al2O3, and 12CaO·7Al2O3, and the content of Na4Ca3(AlO2)10 could reach 92wt% when sintered at 1200°C for 30 min. The main formation stage of Na4Ca3(AlO2)10 occurred at temperatures from 970 to 1100°C, and the content could reach 82wt% when the reaction temperature increased to 1100°C. The crystal system of Na4Ca3(AlO2)10 was tetragonal, and the cells preferred to grow along crystal planes (110) and (210). The formation of Na4Ca3(AlO2)10 was an exothermic reaction that followed a secondary reaction model, and its activation energy was 223.97 kJ/mol. 相似文献
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《矿物冶金与材料学报》2020,27(7):900-909
Ore particles, especially fine interlayers, commonly segregate in heap stacking, leading to undesirable flow paths and changeable flow velocity fields of packed beds. Computed tomography (CT), COMSOL Multiphysics, and MATLAB were utilized to quantify pore structures and visualize flow behavior inside packed beds with segregated fine interlayers. The formation of fine interlayers was accompanied with the segregation of particles in packed beds. Fine particles reached the upper position of the packed beds during stacking. CT revealed that the average porosity of fine interlayers (24.21%) was significantly lower than that of the heap packed by coarse ores (37.42%), which directly affected the formation of flow paths. Specifically, the potential flow paths in the internal regions of fine interlayers were undeveloped. Fluid flowed and bypassed the fine interlayers and along the sides of the packed beds. Flow velocity also indicated that the flow paths easily gathered in the pore throat where flow velocity (1.8 × 10?5 m/s) suddenly increased. Fluid stagnant regions with a flow velocity lower than 0.2 × 10?5 m/s appeared in flow paths with a large diameter. 相似文献
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单工电台接入有线电话网在军事和民用上都有很大的需求,在设计中面临着两个问题,一是有线端二/四转换引入的回波影响,二是话音检测,传统的方案采取自适应顺波抵消技术来解决第一问题,提出了一种基于可靠的话音检测,通过交换控制软件来实现的接入方案,其回顾了自适应回波抵消这一难题,具有软,硬件代价低的优点,该设计方案现已应用于实际的产品中,性能良好。 相似文献
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研究了快速自旋回波产生受激回波的原理,以及受激回波与射频脉冲相位角之间的关系.针对快速自旋回波脉冲序列提出了一种受激回波伪影校正方法.通过两次激发分离出自旋回波与受激回波,然后调整预散相梯度的面积使受激回波与自旋回波中心重合,并修改180°回聚脉冲相位角使受激回波与自旋回波同相位.在1.5T超导磁共振成像系统对校正方法进行了验证,经过受激回波伪影校正后,快速自旋回波图像的信噪比提高了57.08%,图像伪影降低了76.12%.实验结果表明,所提出的方法可以有效抑制受激回波对快速自旋回波成像的影响,提高了图像质量. 相似文献
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基于OpenGL建模技术的航海雷达回波图像生成方法 总被引:1,自引:0,他引:1
为解决当前航海雷达仿真器中雷达回波图像不真实问题,以岸线为例提出基于OpenGL建模技术的模拟航海雷达回波的新方法,研究雷达回波图像生成技术,给出雷达岸线回波及雷达岸线回波图像的生成算法.对RGB、HIS颜色模型在模拟雷达回波强度上的应用进行探讨,给出目标回波强度的数学模型.通过加入噪声模型,实现航海雷达岸线回波仿真,其结果与电子海图显示基本相符. 相似文献
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针对四阶累积量运算量大、运算复杂度高的问题,提出采用峰度与递推算法相结合的方法,降低运算量和硬件实时实现的难度.结合微弱脉冲激光回波信号检测的实际问题,仿真验证了算法的有效性. 相似文献
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针对近年来河南省驻马店市出现的强对流天气,用多普勒天气雷达产品如反射率因子、径向速度、垂直液态含水量、风暴跟踪信息等进行普查分析,重点对两次不同性质的强对流天气的雷达产品进行详细研究.发现强对流天气的雷达回波强度在40 dBz以上,强度为40~50 dBz的回波移速为25~35 km/h时,一般出现强降水,无雷暴和大风;回波移速为35~45 km/h时开始伴有雷暴和大风的出现;当回波移速达到45~60 km/h时,强雷暴和大风的出现几率上升,而强降水的出现几率急剧下降;当回波移速达到60~69 km/h时,则以雷雨大风为主,强降水出现很少.冰雹时强回波伴有"V"型缺口,回波强度可达55 dBz以上,强回波中心出现在9~12 km高度,回波顶可高达15~18km,强回波下方有强上升气流造成的弱回波区.短历时强降水的雷达回波强度比冰雹、雷暴弱,一般为40~50 dBz,强回波中心高度5~6 km;当回波强度大于50 dBz,强回波中心达到8 km以上时,往往伴有强雷电和大风冰雹出现;回波形态多呈现絮状混合型回波,其中有块状的强回波,对流性的强降水回波则是边缘清晰的块状结构. 相似文献
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《云南大学学报(自然科学版)》2013,35(Z1):183-187
利用昭通多普勒雷达资料和区域自动站资料,对2012年昭通雷达探测到的4次冰雹过程进行了综合分析,发现2次冰雹过程属于超级单体风暴,在多普勒雷达回波上都出现了钩状回波和中气旋.另2次冰雹过程属于带状回波冰雹.2次超级单体风暴中气旋均早于钩状回波出现,速度场特征早于强度场特征15~20min,有利于判断风暴的形成和进行风暴的短时预警.超级单体回波强度和对流发展高度都高于带状回波,因而超级单体冰雹灾害强度和面积远大于带状回波冰雹.超级单体风暴移动方向在盛行风向的右侧20°~30°,都是右移超级单体风暴.环境风场特征是决定超级单体风暴移动路径的重要因素,对超级单体风暴冰雹的临近预报有指示作用.低层辐合区和逆风区有利于带状回波的发展和维持. 相似文献
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为在噪声中有效提取水下目标回波,提出一种基于经验模态分解的目标回波提取方法,分别对目标回波与噪声进行经验模态分解,得到二者各阶的固有模态信号分量;计算二者各阶的固有模态分量的能量,求取对应各阶的能量差,并与门限相比较,选取大于门限的固有模态分量重构目标回波信号.分析了经验模态分解阶数和选择门限等因素对重构信号精度的影响.仿真结果表明,该方法可精确提取目标回波.采用该方法提取信号的均方误差均低于自适应滤波方法,尤其在低信噪比时. 相似文献
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在对钢管单面焊对接焊缝进行超声波检测的过程中,会出现多种反射回波。本文通过对超声波检测过程中出现的各种反射回波形成原因及其静态波形和动态波形的特点进行分析,并采用X射线透照方法进行对比,论证了对反射回波分析的可行性和重要性,从而可以有效避免对反射回波的误判。 相似文献